So Farrell recently started using his phone to help him make sense of all the information he collects all day long. "I use a couple of pieces of software on my Android phone, mostly to track blood glucose readings, and also to help me figure out the number of carbohydrates in some food I might be eating," he said. "Because I have to know that in order to give myself the right amount of insulin."

The apps are among thousands that are flooding the market these days. Many are designed to help people take better care of themselves by, for example, counting calories and calculating body mass index.

Some apps, like Runkeeper and MapMyFitness, use the GPS tracker and the accelerometer in your smartphone to help with your exercise routine. Others help people look up symptoms, check drug side effects or locate. Some even measure blood pressure and blood sugar and send the readings off to the doctor.

"Mobile technology is a true game changer for health care," says Dr. Joseph C. Kvedar, founder of the Center for Connected Health in Boston. "It enables us to use that tiny computer in your hand to connect with you at any moment when we need to."

But does somebody need to check these things to make sure they work?

After all, we're not talking about apps that help you find a good restaurant or calculate your mortgage. These apps sometimes help make important decisions — sometimes life-and-death decisions.

"The ones that worry me are ones for instance where you can take an image of a skin lesion and then map it back to a database in the cloud and be told whether it should be evaluated for a melanoma or not," says Kvedar, a dermatologist by training. "It just seems a little scary right how to have software making decisions about moles."

As a result, the Food and Drug Administration has concluded that at least some apps should undergo review by the agency before being permitted on the market. "There are many mobile apps that are on the market that are medical devices," Dr. Jeffrey Shuren, who heads the FDA's Center for Devices and Radiological Health. "There are apps today that change a mobile platform into an EKG machine. When it's being used to diagnose patients, it's a medical device we believe subject to FDA oversight."

But Shuren stresses that the FDA has no plans to review most apps, such as those that help with wellness, healthier lifestyles. Same goes for thoseused to help patients manage their medical conditions. "The risk to patients are very, very low," he says.

Some app makers, however, say they can't be sure what's allowed. "The problem is now we live in this era of connected health where everything is being connected to everything else," said Bradley Merrill Thompson, a lawyer who represents some app makers. "So now that you've got this ecosystem where everything is connected to everything else. That's what creates this ambiguity with FDA."

Some worry that even the possibility of regulation will stifle innovation. "If FDA steps into this field it's going to create so much uncertainty for product developers that it's going to discourage a lot of investment and it's going to discourage a lot of programmers from getting into this space," said Dr. Scott Gottlieb of the American Enterprise Institute.

Shuren and other FDA officials said the agency is trying to walk a fine line between protecting patients without stifling innovation. By the end of the year, the agency hopes clarify how it will handle the explosion of mobile medical apps.

Copyright 2012 National Public Radio. To see more, visit http://www.npr.org/.

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